Encryption method, encryptor, and encryption system for encrypting electronic data by splitting electronic data

ABSTRACT

An encryption method includes displaying encryption target data on a display screen as an image, performing first acceptance in which designation of an at least partial region of the displayed image is accepted, performing second acceptance in which designation regarding splitting of the designated at least partial region is accepted, and splitting data that is included in the encryption target data and corresponds to the designated at least partial region in accordance with the designation regarding the splitting under a secret sharing scheme.

BACKGROUND

1. Technical Field

The present disclosure relates to an encryption method and the like forencrypting electronic data by splitting the electronic data.

2. Description of the Related Art

The necessity of safely retaining and managing electronic informationhas been increasing in recent years. Particularly in cloud computing orthe like, where diverse services are provided from servers via networks,leakage of information sent out on the networks, etc. may easily occur.Various techniques are suggested so as to prevent such leakage ofinformation (see, for example, Japanese Unexamined Patent ApplicationPublication No. 2008-193612).

A known technique to prevent information from leaking out is a secretsharing scheme (threshold secret sharing scheme), by which secret dataincluding important information is distributed to be n pieces ofdistributed data and the secret data can be decoded (reconstructed) onlywhen k, which is a threshold, or more pieces of the n pieces ofdistributed data are collected.

In a secret sharing scheme, generally, data is split uniformlyregardless of the content of the data.

SUMMARY

One non-limiting and exemplary embodiment provides an encryption methodand the like, which enable designation regarding splitting of specificpart of data, which is for example, part included in the data and hashigh confidentiality, such as designation of the number of splits, to beperformed easily.

In one general aspect, the techniques disclosed here feature anencryption method using a secret sharing scheme, the encryption methodincluding: displaying encryption target data on a display screen as animage; performing first acceptance in which designation of an at leastpartial region of the displayed image is accepted; performing secondacceptance in which designation regarding splitting of the designated atleast partial region is accepted; and splitting data that is included inthe encryption target data and corresponds to the designated at leastpartial region in accordance with the designation regarding thesplitting under the secret sharing scheme.

According to the encryption method of the present disclosure,designation regarding splitting of specific part of data can be easilyperformed.

It should be noted that general or specific embodiments may beimplemented as a system, a device, an integrated circuit, a computerprogram, a recording medium, such as a computer-readable compactdisc-read-only memory (CD-ROM), or any selective combination thereof.

Additional benefits and advantages of the disclosed embodiments willbecome apparent from the specification and drawings. The benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the specification and drawings, which need not all beprovided in order to obtain one or more of such benefits and/oradvantages.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration for explaining an encryption methodaccording to Embodiment 1 in outline;

FIG. 2 is an illustration for explaining data splitting of an encryptoraccording to Embodiment 1;

FIG. 3 is an illustration for explaining the data splitting of theencryptor according to Embodiment 1;

FIG. 4 is a block diagram that illustrates a functional structure of theencryptor according to Embodiment 1;

FIG. 5 is a flow chart that illustrates operations of the encryptoraccording to Embodiment 1;

FIG. 6 is a diagram for explaining splitting of encryption target data;

FIG. 7 is an illustration of an example in which the number of splits isdesignated in accordance with the number of taps on a display screen;

FIG. 8 is an illustration of an example in which the number of splits isdesignated in accordance with the position of a knob of a graphical userinterface (GUI) of a slider;

FIG. 9 is an illustration for explaining an example of a method ofchanging the number of splitting lines based on a splitting line inaccordance with the position of the knob of the slider;

FIG. 10 is an illustration of an example in which the number of splitsis designated through handwriting input of a numeral onto the displayscreen;

FIG. 11 is an illustration of an example in which the number of splitsis designated through handwriting input of a splitting line onto thedisplay screen;

FIG. 12 is a block diagram that illustrates a functional structure of anencryption system;

FIG. 13 is a flow chart that illustrates operations of an informationcommunication terminal; and

FIG. 14 is a flow chart that illustrates operations of a client server.

DETAILED DESCRIPTION

An encryption method according to an aspect of the present disclosureuses a secret sharing scheme and includes: displaying encryption targetdata on a display screen as an image; performing first acceptance inwhich designation of an at least partial region of the displayed imageis accepted; performing second acceptance in which designation regardingsplitting of the designated at least partial region is accepted; andsplitting data that is included in the encryption target data andcorresponds to the designated at least partial region in accordance withthe designation regarding the splitting under the secret sharing scheme.

Thus, a user can easily perform designation regarding splitting onspecific part included in the encryption target data through the displayscreen.

In the second acceptance, at least one of the number of splits and athreshold indicating the number of pieces of the encryption target dataafter the splitting, which is necessary for decoding, may be accepted asthe designation regarding the splitting.

Thus, a user can easily designate at least one of the number of splitsand the threshold for specific part included in the encryption targetdata through the display screen.

In the second acceptance, the number of taps on the display screen maybe accepted as the number of splits or the threshold, and in thedisplaying the encryption target data, the number of taps may be furtherdisplayed on the display screen.

Thus, a user can easily designate the number of splits or the thresholdof specific part included in the encryption target data through thetapping operation on the display screen.

In the second acceptance, a count value obtained by counting up for aduration of a long push against the display screen may be accepted asthe number of splits or the threshold, and in the displaying theencryption target data, the count value may be further displayed on thedisplay screen.

Thus, a user can easily designate the number of splits or the thresholdof specific part included in the encryption target data by the long pushoperation on the display screen.

In the second acceptance, a numeral provided through handwriting inputonto the display screen may be accepted as the number of splits or thethreshold, and in the displaying the encryption target data, the numeralmay be further displayed on the display screen.

Thus, a user can easily designate the number of splits or the thresholdof specific part included in the encryption target data through thehandwriting input of a numeral onto the display screen.

In the second acceptance, the number of regions caused by a splittingline provided through handwriting input in the at least partial regionon the display screen may be accepted as the number of splits, and inthe displaying the encryption target data, the splitting line may befurther displayed on the display screen.

Thus, a user can easily designate the number of splits of specific partincluded in the encryption target data through the handwriting input ofa splitting line onto the display screen. When the splitting line isdisplayed on the display screen in this manner, the user can visuallyrecognize the degree of the splitting.

In the displaying the encryption target data, a graphical user interface(GUI) of a slider may be further displayed on the display screen, and inthe second acceptance, a value specified by a position of a knob of theslider may be accepted as the number of splits or the threshold.

Thus, a user can easily designate the number of splits or the thresholdof specific part included in the encryption target data through thedragging operation on the knob of the slider.

In the splitting the data, data that is included in the encryptiontarget data and corresponds to a remaining region other than thedesignated at least partial region may be further split by apredetermined method using a secret sharing scheme.

In the second acceptance, designation regarding splitting of a remainingregion other than the designated at least partial region may be furtheraccepted, and in the splitting the data, data that is included in theencryption target data and corresponds to the remaining region may besplit in accordance with the designation regarding the splitting of theremaining region under a secret sharing scheme.

The encryption method may further include causing the split encryptiontarget data to be stored in a plurality of server devices throughdistribution.

The secret sharing scheme is an encryption scheme, in which target datais split into data pieces so that the number of data pieces of the splittarget data is equal to or larger than a threshold, and decoding of thetarget data using the data pieces is impossible when the number of datapieces is smaller than the threshold.

An encryptor according to an aspect of the present disclosure uses asecret sharing scheme and includes: a display control unit that outputsinformation for displaying encryption target data on a display screen asan image; a first acceptance unit that accepts designation of an atleast partial region of the displayed image; a second acceptance unitthat accepts designation regarding splitting of the designated at leastpartial region; and a splitting unit that splits data included in theencryption target data and corresponding to the designated at leastpartial region in accordance with the designation regarding thesplitting under the secret sharing scheme.

An encryption system according to an aspect of the present disclosureuses a secret sharing scheme and includes: an information communicationterminal; and a server, the information communication terminalincluding: a reception unit that receives information for displayingencryption target data as an image from the server; a display unit thatdisplays the image based on the information; a first acceptance unitthat accepts designation of an at least partial region of the displayedimage; a second acceptance unit that accepts designation regardingsplitting of the designated at least partial region; and a transmissionunit that transmits the designation of the at least partial region andthe designation regarding the splitting to the server, the serverincluding: a server transmission unit that transmits the information tothe information communication terminal; a server reception unit thatreceives the designation of the at least partial region and thedesignation regarding the splitting from the information communicationterminal; and a splitting unit that splits data included in theencryption target data and corresponding to the designated at leastpartial region in accordance with the designation regarding thesplitting under the secret sharing scheme.

It should be noted that general or specific embodiments may beimplemented as a system, a device, an integrated circuit, a computerprogram, a recording medium, such as a computer-readable compactdisc-read-only memory (CD-ROM), or any selective combination thereof.

Embodiments are described in detail below with reference to thedrawings.

All of the embodiments described below provide general or specificexamples. The values, shapes, materials, constituent elements,arrangement positions of the constituent elements, connection forms,steps, order of the steps, and the like that are indicated below in theembodiments are mere examples and are not intended to limit the presentdisclosure. Among the constituent elements of the embodiments below, theconstituent elements that are not recited in the independent claimsindicating the most superordinate concepts can be explained as givenconstituent elements.

Each drawing is a schematic diagram, which is not necessarilyillustrated precisely. In the drawings, the same references are given tosubstantially the same constituent elements and overlapping explanationon such constituent elements may be omitted or simplified.

Embodiment 1

[Outline of Encryption Method]

An encryption method (a secret sharing process) of data that anencryptor 10 according to Embodiment 1 performs is described in outlinefirst. FIG. 1 is a schematic illustration for explaining the outline ofthe encryption method.

The encryptor 10 is a device that splits encryption target data 30 inaccordance with the secret sharing scheme, distributes the split data tocloud servers 20 a and 20 b, and causes the split data to be stored inthe cloud servers 20 a and 20 b. In the example of FIG. 1, the encryptor10 splits the encryption target data 30 into split data 30 a and splitdata 30 b, and distributes and transmits the split data 30 a and thesplit data 30 b to the cloud servers 20 a and 20 b. That is, theencryption target data 30 is distributed to and stored in the cloudservers 20 a and 20 b.

The secret sharing scheme (threshold secret sharing scheme) is anencryption scheme, in which target data is split into data pieces sothat the number of data pieces of the split target data is equal to orlarger than a threshold, and decoding of the target data using the datapieces is impossible when the number of data pieces is smaller than thethreshold.

In the encryptor 10, the above-described splitting of data is performedin accordance with input onto an image displayed on a display screen 40.FIGS. 2 and 3 are illustrations for explaining the data splitting of theencryptor 10.

In the encryption, the encryption target data 30 is displayed on thedisplay screen 40 of a display unit 15 of the encryptor 10 as an image50. In Embodiment 1, the encryption target data 30, which is the image50, is a still image including a photograph region 60 in which a facephotograph is positioned.

When for example, the photograph region 60 has high confidentiality fora user, first of all, the user designates a portion that is included inthe photograph region 60 and corresponds to the face as a target region61 as illustrated in FIG. 3(a). The portion other than the target region61 is referred to as a non-target region 62. After that, the userdesignates the number of splits of the target region 61 as illustratedin FIG. 3(b).

On accepting the designation of the target region 61 and the designationof the number of splits from the user, the encryptor 10 splits theencryption target data 30 corresponding to the target region 61 intopieces of the designated number of splits. Then, the encryptor 10distributes and transmits the encryption target data 30 after thesplitting to a plurality of cloud servers, which are the cloud servers20 a and 20 b.

Thus, with the encryptor 10, a user can readily designate the part ofthe encryption target data 30, for which the user desires to designatethe number of splits, and the number of splits through the displayscreen 40 (the display unit 15). That is, a user can easily designatethe number of splits of specific part included in the encryption targetdata 30.

[Structure and Operations of Encryptor]

A structure and operations of the encryptor 10 are described next, FIG.4 is a block diagram that illustrates a functional structure of theencryptor 10. FIG. 5 is a flow chart that illustrates the operations ofthe encryptor 10.

As illustrated in FIG. 4, the encryptor 10 includes an input acceptanceunit 11, a detection unit 12, a region splitting unit 13, anumber-of-splits setting unit 14, the display unit 15, a split datageneration unit 16, a split data transmission unit 17, and a storageunit 18. FIG. 4 further illustrates a plurality of cloud servers, whichare the cloud servers 20 a and 20 b through a cloud server 20 n, and thecloud server 20 a includes a split data reception unit 21 and a splitdata retaining unit 22. The cloud servers 20 b to 20 n each have astructure similar to the structure of the cloud server 20 a. The numberof the cloud servers 20 b to 20 n is not particularly limited.

The encryptor 10 is a device that splits the encryption target data 30in accordance with the secret sharing scheme. Specifically, theencryptor 10 is an information communication terminal, such as apersonal computer, a smartphone, a tablet terminal, or a server.

The display unit 15 causes the encryption target data 30 to be displayedon the display screen 40 as the image 50 (S11 in FIG. 5). Specifically,the display unit 15 is a display panel (a display device), such as aliquid crystal panel or an organic electroluminescent (EL) panel. Theencryption target data 30 is stored in the storage unit 18 for example.

The display unit 15 may be provided as a separate display device outsidethe encryptor 10. In such a case, the encryptor 10 includes a displaycontrol unit instead of the display unit 15 and the display control unitoutputs display information for causing the encryption target data 30 tobe displayed on the display screen 40 of the display device providedoutside as an image to the display device.

The input acceptance unit 11 is an example of the first acceptance unitand accepts designation of the target region 61, which is an at leastpartial region of the displayed image 50 (S12 in FIG. 5). Also, theinput acceptance unit 11 is an example of the second acceptance unit andaccepts designation regarding the splitting of the designated targetregion 61 (S13 in FIG. 5). The input acceptance unit 11 may include afunction of the detection unit 12.

Although in Embodiment 1, the input acceptance unit 11 accepts thedesignation of the number of splits as the above-described designationregarding the splitting, the input acceptance unit 11 may accept thedesignation of a threshold instead of or in addition to the number ofsplits. That is, the input acceptance unit 11 accepts at least one ofthe designation of the number of splits and the designation of athreshold. The threshold is a value that indicates the number of piecesof the encryption target data 30 after the splitting, which arenecessary for decoding.

Although in Embodiment 1, the input acceptance unit 11 is a touch panelthat accepts input of a user onto the display screen 40 using a fingeror a stylus, the input acceptance unit 11 may be any device only whenthe device functions as an input interface, such as a mouse or akeyboard.

The detection unit 12 detects the input of the user onto the inputacceptance unit 11. The detection unit 12 is specifically a processor, amicrocomputer, a dedicated circuit, or the like.

The region splitting unit 13 splits the image 50 into the target region61 and the non-target region 62 in accordance with the designation ofthe target region 61 detected by the detection unit 12, and causes thedisplay unit 15 to display the target region 61. The region splittingunit 13 is specifically a processor, a microcomputer, a dedicatedcircuit, or the like.

In the above-described example of FIG. 3, the display unit 15 displaysthe target region 61 of the image 50 in accordance with the control (acontrol signal) of the region splitting unit 13 by surrounding thetarget region 61 with a line and changing the hue of the target region61. The target region 61 may be displayed in any manner only when themanner enables the user who visually recognizes the display unit 15 tosense the target region 61.

The number-of-splits setting unit 14 causes the display unit 15 todisplay the number of splits in accordance with the number of splitsdetected by the detection unit 12. The region splitting unit 13 isspecifically a processor, a microcomputer, a dedicated circuit, or thelike.

The number-of-splits setting unit 14 may cause the number of splits tobe displayed in characters in the above-described example of FIG. 3 ormay cause a splitting line to be displayed as described below. Thenumber of splits may be displayed in any manner only when the mannerenables the user who visually recognizes the display unit 15 to sensethe number of splits.

The split data generation unit 16 splits the data that is included inthe encryption target data 30 and corresponds to the designated targetregion 61 in accordance with the user's designation regarding thesplitting under the secret sharing scheme (S14 in FIG. 5). The splitdata generation unit 16 splits the data corresponding to the non-targetregion 62, which is the region other than the designated target region61, by a predetermined method. The split data generation unit 16 is anexample of the splitting unit and is specifically a processor, amicrocomputer, a dedicated circuit, or the like. The information on theposition of the target region 61, the number of splits, and the like areoutput from the detection unit 12 to the split data generation unit 16through the number-of-spots setting unit 14.

Further, the split data generation unit 16 generates correlationinformation that indicates the correlation between the encryption targetdata 30 corresponding to the target region 61 and the encryption targetdata 30 corresponding to the non-target region 62, and causes thegenerated correlation information to be stored in the storage unit 18.The correlation information is used in decoding the encryption targetdata 30, and is for example, table format information or may beinformation in another format.

The split data transmission unit 17 transmits the encryption target data30 after the splitting, which is hereinafter also referred to as thesplit data, to the plurality of cloud servers 20 a to 20 n (S15 in FIG.5). As a result, the split encryption target data 30 are stored throughdistribution. Although the split data transmission unit 17 isspecifically a general-purpose communication module (communicationcircuit), the split data transmission unit 17 is not particularlylimited. The split data transmission unit 17 may perform communicationusing any wire or wireless communication scheme (communicationstandard).

The storage unit 18 stores the encryption target data 30, theabove-described correlation information, and the like. Specifically, thestorage unit 18 is a storage device, such as a hard disk drive (HDD) orsemiconductor memory. The storage unit 18 may be provided as a separatestorage device outside the encryptor 10.

The cloud servers 20 a to 20 n are examples of the server device andretain the split data.

The split data reception unit 21 receives the split data from the splitdata transmission unit 17. The split data reception unit 21 may performcommunication using any wire or wireless communication scheme(communication standard).

The split data retaining unit 22 is a storage device in which the splitdata received by the split data reception unit 21 is stored. The splitdata retaining unit 22 is specifically a storage device, such as an HDDor semiconductor memory.

[Details of Encryption Method]

Described below are details of the encryption method that the encryptor10 performs, that is, the splitting of the encryption target data 30.FIG. 6 is a diagram for explaining the splitting of the encryptiontarget data 30.

As described above, in the encryptor 10, the designation of the targetregion 61 and the designation of the number of splits of the targetregion 61 are performed on the encryption target data 30 displayed asthe image 50. In the example of FIG. 6, the number of splits of thetarget region 61 is designated as ten. Accordingly, the split datageneration unit 16 of the encryptor 10 splits data (pixel data) that isincluded in the encryption target data 30 and corresponds to the targetregion 61 into ten pieces of split data, and distributes and transmitsthe ten pieces of split data to the plurality of cloud servers 20 a to20 n.

The non-target region 62 that is included in the image 50 and is notdesignated by the user is split by a predetermined method using thesecret sharing scheme. In the example of FIG. 6, the split datageneration unit 16 of the encryptor 10 splits data (pixel data)corresponding to the non-target region 62 into seven pieces of splitdata, and distributes and transmits the seven pieces of split data tothe plurality of cloud servers 20 a to 20 n.

Constitution information indicating that the ten pieces of split dataconstitute the encryption target data 30 corresponding to the targetregion 61 is managed by the cloud servers 20 a to 20 n. Similarly,constitution information indicating that the seven pieces of split dataconstitute the encryption target data 30 corresponding to the non-targetregion 62 is managed by the plurality of cloud servers 20 a to 20 n.

The correlation information indicating the correlation between theencryption target data 30 corresponding to the target region 61, whichis the data before the splitting of the ten pieces of split data, andthe encryption target data 30 corresponding to the non-target region 62,which is the data before the splitting of the seven pieces of splitdata, is stored in the storage unit 18. In decoding the encryptiontarget data 30, such correlation information and the above-describedconstitution information are used to collect the split data.

In the description of FIG. 6 above, the encryption target data 30corresponding to the non-target region 62 is split by the predeterminedmethod. However, similar to the encryption target data 30 correspondingto the target region 61, the encryption target data 30 corresponding tothe non-target region 62 may be split in accordance with the user'sdesignation regarding the splitting under a secret sharing scheme. Theencryption target data 30 corresponding to the non-target region 62 mayremain unsplit.

[Designation of Target Region and Designation of Number of Splits]

A method of designating the target region 61 and a method of designatingthe number of splits are described below.

The designation of the target region 61 is performed by surrounding adesired region through, for example, a dragging operation on the displayscreen 40 of the display unit 15, which is an operation of putting afinger onto the display screen 40 and moving the finger without takingthe put finger off the display screen 40. The designation method of thetarget region 61 is not limited to the above-described method and thetarget region 61 may be designated in any manner.

Various methods are conceivable for the designation of the number ofsplits. The number of splits is designated in accordance with, forexample, the number of taps on the display screen 40 of the display unit15. FIG. 7 is an illustration of an example in which the number ofsplits is designated in accordance with the number of taps on thedisplay screen 40. In FIG. 7, only the photograph region 60 of the image50 is illustrated.

When the number of splits is designated in accordance with the number oftaps on the display screen 40, the input acceptance unit 11 accepts thenumber of taps on the display screen 40 as the number of splits. Asillustrated in FIG. 7(a)-(c), on the basis of the control of thenumber-of-splits setting unit 14, the display unit 15 causes the numberof taps to be displayed on the display screen 40 as the number ofsplits. Although the position on the display screen 40 at which the tapis performed is not particularly limited, for example, only a tap in thetarget region 61 may be detected as a valid tap.

Thus, a user can easily designate the number of splits of specific partincluded in the encryption target data 30 through the tapping operationon the display screen 40.

The number of splits may be designated according to the duration of thelong push against the display screen 40. In this case, the inputacceptance unit 11 accepts a count value obtained by counting up orcounting down for the duration of the long push (touch) against thedisplay screen 40 as the number of splits. After that, the display unit15 causes the count value to be displayed on the display screen 40 asthe number of splits on the basis of the control of the number-of-splitssetting unit 14. Although the position on the display screen 40 at whichthe long push is performed is not particularly limited, for example,only a long push in the target region 61 may be detected as a valid longpush.

Thus, a user can easily designate the number of splits of specific partincluded in the encryption target data 30 through the long pushoperation on the display screen 40.

The number of splits may be designated according to the position of aknob 71 of a GUI of a slider 70 displayed on the display screen 40. FIG.8 is an illustration of an example in which the number of splits isdesignated according to the position of the knob 71 of the slider 70 ofthe GUI. In FIG. 8, only the photograph region 60 of the image 50 isillustrated and FIG. 8 is described below under the assumption that theentire photograph region 60 constitutes the target region.

In the example of FIG. 8, the display unit 15 causes the slider 70,which is a GUI of a slider, to be displayed on the display screen 40,and the input acceptance unit 11 accepts a value specified according tothe position of the knob 71 of the slider 70 as the number of splits.After that, the display unit 15 causes the number of splits to bedisplayed on the display screen 40 on the basis of the control of thenumber-of-splits setting unit 14. The position on the display screen 40at which the slider 70 is displayed is not particularly limited, buttypically, the slider 70 is displayed near the target region, which isthe photograph region 60 in FIG. 8.

The number of splits may be displayed as a numeral or, as illustrated inFIG. 8, a splitting line may be displayed. In this case, when a userchanges the position of the knob 71 of the slider 70 though a draggingoperation as illustrated in FIG. 8(a)-(c), the number of splits (thenumber of splits based on the splitting lines) increases or decreases,depending on the position of the knob 71.

A method of changing the number of splits based on the splitting linesin accordance with the position of the knob 71 of the slider 70 isdescribed in detail below with reference to FIG. 9. FIG. 9 is anillustration for explaining an example of the method of changing thenumber of splits based on the splitting lines in accordance with theposition of the knob 71 of the slider 70.

In the example of FIG. 9, points of the number dependent on the positionof the slider 70 are set for each side of the photograph region 60. Forexample, two points are set for each side as illustrated in FIG. 9(a).The points may be randomly positioned at this time.

After that, corresponding points are connected by a straight line or acurved line. The corresponding points mentioned here are points 63 and64 for example. That is, in connecting the points provided on the twosides extending in the upward and downward directions, which face eachother, the points having the same positional rank (in other words, thepoints ordered to be equivalent in the respective sequences) whencounted from the upper side of each side serve as the correspondingpoints.

As illustrated in FIG. 9(b), the corresponding points are connectedunder the constraint that lines in the lateral direction do not crosseach other and lines in the longitudinal direction do not cross eachother. The corresponding points may be connected in any manner as longas this constraint is ensured.

Accordingly, a user may easily designate the number of splits ofspecific part included in the encryption target data 30 through adragging operation for the knob 71 of the slider 70. When the splittinglines are displayed on the display screen 40 in this manner, a user canvisually recognize the degree of the splitting.

The number of splits may be designated through handwriting input of anumeral onto the display screen 40. FIG. 10 is an illustration of anexample in which the number of splits is designated through handwritinginput of a numeral onto the display screen 40. In FIG. 10, only thephotograph region 60 of the image 50 is illustrated.

When the number of splits is designated through handwriting input of anumeral onto the display screen 40, the input acceptance unit 11 acceptsthe numeral provided through the handwriting input onto the displayscreen 40 as the number of splits. Then, as illustrated in FIG. 10, thedisplay unit 15 causes the numeral provided through the handwritinginput to be displayed on the display screen 40. Although the position(range) on the display screen 40, which allows the handwriting input tobe valid, is not particularly limited, for example, only handwritinginput in the target region may be regarded as valid.

Thus, a user can easily designate the number of splits of specific partincluded in the encryption target data 30 through the handwriting inputof a numeral onto the display screen 40.

The number of splits may be designated through the handwriting input ofsplitting lines onto the display screen 40. FIG. 11 is an illustrationof an example in which the number of splits is designated throughhandwriting input of a splitting line onto the display screen 40. InFIG. 11, only the photograph region 60 of the image 50 is illustrated.

When the number of splits is designated through the handwriting input ofa splitting line onto the display screen 40, the input acceptance unit11 accepts the number of regions split by the splitting line providedthrough the handwriting input onto the target region of the displayscreen 40, which is the photograph region 60 in FIG. 11, as the numberof splits. Then, as illustrated in FIG. 11, the display unit 15 causesthe splitting lines provided through the handwriting input to bedisplayed on the display screen 40.

Thus, a user can easily designate the number of splits of specific partincluded in the encryption target data 30 through the handwriting inputof a splitting line onto the display screen 40.

When a user inputs a splitting line by handwriting, the number ofsplits, and the shapes and sizes of the regions after the splitting areset freely, and accordingly, it may be difficult to generate split datathat corresponds to each region of the image 50 split through thehandwriting input. In such a case, when the encryption target data 30corresponding to the target region is split into pieces of the number ofsplits specified by the splitting lines, it is allowed that the splitdata does not completely correspond to each region of the image splitthrough the handwriting input.

The method of designating the target region 61 and the method ofdesignating the number of splits are described above. As describedabove, the input acceptance unit 11 may accept the designation of athreshold instead of or in addition to the number of splits, and also inthe case in which a threshold is accepted, a structure similar to thestructure employed in the case in which the number of splits isaccepted. In accepting a threshold, normally, neither the designation ofa threshold through handwriting input of a splitting line nor thedisplay of a splitting line by the display unit 15 is performed.

[Recapitulation]

As described above, the encryptor 10 causes the encryption target data30 to be displayed on the display screen 40 as the image 50 and acceptsthe designation of the target region 61, which is an at least partialregion of the displayed image 50. The encryptor 10 further accepts thedesignation regarding the splitting of the designated target region 61and splits the data that is included in the encryption target data 30and corresponds to the designated target region 61 in accordance withthe designation regarding the splitting under the secret sharing scheme.

Thus, a user can easily designate the number of splits of specific partincluded in the encryption target data 30.

[Variation]

The present disclosure may be implemented as an encryption system thatincludes an information communication terminal and a client server.Described below are a structure and operations of an encryption system100. FIG. 12 is a block diagram that illustrates a functional structureof the encryption system 100. FIG. 13 is a flow chart that illustratesoperations of an information communication terminal 110. FIG. 14 is aflow chart that illustrates operations of a client server 120.Overlapping explanation on the constituent elements substantially thesame as the constituent elements already described in Embodiment 1 maybe omitted below.

The encryption system 100 illustrated in FIG. 12 is an encryption systemusing a secret sharing scheme, and includes the informationcommunication terminal 110 and the client server 120.

The information communication terminal 110 includes a communication unit111, a display unit 112, an input acceptance unit 113, and a controlunit 114. For example, the information communication terminal 110 is apersonal computer, a smartphone, or a tablet terminal.

The communication unit 111 receives display information for displayingan encryption target data 30 as an image 50 from a server communicationunit 121 of the client server 120 (S21 in FIG. 13). Further, thecommunication unit 111 transmits designation of a target region 61 anddesignation regarding splitting to the server communication unit 121 ofthe client server 120 (S25 in FIG. 13). The communication unit 111 is anexample of the reception unit and the transmission unit and isspecifically a general-purpose communication module (communicationcircuit) or the like.

The display unit 112 displays the image 50 based on the received displayinformation (S22 in FIG. 13). The display unit 112 is specifically adisplay panel (display device), such as a liquid crystal panel or anorganic EL panel. The display information is output from the servercommunication unit 121 to the display unit 112 through the control unit114.

The input acceptance unit 113 accepts designation of the target region61, which is an at least partial region of the displayed image 50 (323in FIG. 13). Further, the input acceptance unit 113 accepts designationregarding the splitting of the designated target region 61 (S24 in FIG.13). The input acceptance unit 113 is an example of the first acceptanceunit and the second acceptance unit, and is specifically a touch panelor the like.

The control unit 114 performs control regarding the informationcommunication terminal 110, which includes communication control of thecommunication unit 111, display control of the display unit 112, anddetection of input onto the input acceptance unit 113. The control unit114 is specifically a processor, a microcomputer, a dedicated circuit,or the like.

The client server 120 is an example of the server, and includes theserver communication unit 121, a server control unit 122, and a storageunit 123.

The server communication unit 121 transmits display information to thecommunication unit 111 of the information communication terminal 110(S31 in FIG. 14). For example, the display information is generated bythe server control unit 122 using the encryption target data 30 storedin the storage unit 123 and the display information includes informationfor displaying the target region 61, the number of splits, and thesplitting lines on the display screen 40, which are described above.

Further, the server communication unit 121 receives the designation ofthe target region 61 and the designation regarding the splitting fromthe communication unit 111 of the information communication terminal 110(S32 in FIG. 14). In addition, the server communication unit 121distributes and transmits the split encryption target data 30 to aplurality of cloud servers 20 a to 20 n (334 in FIG. 14). The servercommunication unit 121 is an example of the server transmission unit andthe server reception unit, and is specifically a general-purposecommunication module (communication circuit).

The server control unit 122 performs control regarding the informationcommunication terminal 110, such as communication control of the servercommunication unit 121. The server control unit 122 splits the data thatis included in the encryption target data 30 and corresponds to thedesignated target region 61 in accordance with the designation regardingthe splitting under the secret sharing scheme (S33 in FIG. 14). Theserver control unit 122 is an example of the splitting unit and isspecifically a processor, a microcomputer, a dedicated circuit, or thelike.

The storage unit 123 stores the encryption target data 30, correlationinformation as is described above, and the like. The storage unit 123 isspecifically a storage device, such as an HDD or semiconductor memory.The information communication terminal 110 may include a similar storageunit.

The above-described encryption system 100 also enables the number ofsplits of specific part included in the encryption target data 30 to beeasily designated, similar to the encryptor 10.

The present disclosure may be implemented as an encryptor thatcorresponds to the client server 120 in the encryption system 100. Inthis case, the server communication unit 121 corresponds to the firstacceptance unit and the second acceptance unit, and the server controlunit 122 corresponds to the display control unit and the splitting unit.

Other Embodiments

Although the encryption method, the encryptor, and the encryption systemaccording to the embodiments are described above, the present disclosureis not limited to the above-described embodiments.

Although it is explained in the above-described embodiments that theencryption target data 30 is a still image, for example, the encryptiontarget data 30 may be a moving image, text data, or the like. Theencryption target data 30 may be any data only when the data can bedisplayed on the display screen 40 as the image 50.

In each of the above-described embodiments, each constituent element maybe configured with dedicated hardware or may be implemented by executinga software program suitable for each constituent element. Eachconstituent element may be implemented by a program execution unit, suchas a central processing unit (CPU) or a processor, reading a softwareprogram recorded in a recording medium, such as a hard disk orsemiconductor memory, and executing the software program.

The constituent elements may be circuits. Such circuits may make up asingle circuit as a whole or may be separate circuits. Each of thecircuits may be a general-purpose circuit or may be a dedicated circuit.

Although the encryption method, the encryptor, and the encryption systemaccording to one or more aspects based on the embodiments are describedabove, the present disclosure is not limited to the embodiments. As longas the spirit of the present disclosure is not departed, an embodimentin which each kind of variations that those skilled in the art canconceive is applied to the present embodiment or an embodiment obtainedby combining constituent elements according to a different embodimentmay also be included in the scope of the one or more aspects.

The present disclosure is applicable to cloud computing or the like asan encryption method using a secret sharing scheme, which enables thenumber of splits of specific part included in data to be easilydesignated.

What is claimed is:
 1. An encryption method using a secret sharing scheme, the encryption method comprising: displaying encryption target data on a display screen as an image; performing first acceptance in which designation of an at least partial region of the displayed image is accepted; performing second acceptance in which designation regarding splitting of the designated at least partial region is accepted; and splitting data in accordance with the designation regarding the splitting under the secret sharing scheme, the data (i) included in the encryption target data, and (ii) corresponding to the designated at least partial region, wherein in the second acceptance, at least one of the number of splits and a threshold indicating the number of pieces of the encryption target data after the splitting is accepted as the designation regarding the splitting, the number of pieces of the encryption target data after the splitting being necessary for decoding, wherein in the second acceptance, a count value obtained by counting up for a duration of a long push against the display screen is accepted as the number of splits or the threshold, and wherein in the displaying the encryption target data, the count value is further displayed on the display screen.
 2. The encryption method according to claim 1, wherein in the splitting the data, data that is included in the encryption target data and corresponds to a remaining region other than the designated at least partial region is further split by a predetermined method using a secret sharing scheme.
 3. The encryption method according to claim 1, wherein in the second acceptance, designation regarding splitting of a remaining region other than the designated at least partial region is further accepted, and in the splitting the data, data that is included in the encryption target data and corresponds to the remaining region is split in accordance with the designation regarding the splitting of the remaining region under a secret sharing scheme.
 4. The encryption method according to claim 1, further comprising: causing the split encryption target data to be stored in a plurality of server devices through distribution.
 5. The encryption method according to claim 1, wherein the secret sharing scheme is an encryption scheme, in which target data is split into data pieces so that the number of data pieces of the split target data is equal to or larger than a threshold, and decoding of the target data using the data pieces is impossible when the number of data pieces is smaller than the threshold.
 6. An encryptor using a secret sharing scheme, the encryptor comprising: a processor; and a non-transitory recording medium having a computer program, the computer program which when executed by the processor, causes the processor to perform operations including displaying encryption target data on a display screen as an image; performing first acceptance in which designation of an at least partial region of the displayed image is accepted; performing second acceptance in which designation regarding splitting of the designated at least partial region is accepted; and splitting data in accordance with the designation regarding the splitting under the secret share scheme, the data (i) included in the encryption target data, and (ii) corresponding to the designated at least partial region, wherein in the second acceptance, at least one of the number of splits and a threshold indicating the number of pieces of the encryption target data after the splitting is accepted as the designation regarding the splitting, the number of pieces of the encryption target data after the splitting being necessary for decoding, wherein in the second acceptance, a count value obtained by counting up for a duration of a long push against the display screen is accepted as the number of splits or the threshold, and wherein in the displaying the encryption target data, the count value is further displayed on the display screen.
 7. An encryption system using a secret sharing scheme, the encryption system comprising: an information communication terminal; and a server, the information communication terminal including a first processor; and a first non-transitory recording medium having a first computer program, which when executed by the first processor, causes the first processor to perform operations including receiving encryption target data as an image from the server; displaying the encryption target data on a display screen as the image; performing first acceptance in which designation of an at least partial region of the displayed image is accepted; performing second acceptance in which designation regarding splitting of the designated at least partial region is accepted; and transmitting the designation of the at least partial region and the designation regarding the splitting to the server, the server including a second processor; and a second non-transitory recording medium having a second computer program, which when executed by the second processor, causes the second processor to perform operations including transmitting the encryption target data to the information communication terminal; receiving the designation of the at least partial region and the designation regarding the splitting from the information communication terminal; and splitting data in accordance with the designation regarding the splitting under the secret sharing scheme, the data (i) included in the encryption target data, and (ii) corresponding to the designated at least partial region, wherein in the second acceptance, at least one of the number of splits and a threshold indicating the number of pieces of the encryption target data after the splitting is accepted as the designation regarding the splitting, the number of pieces of the encryption target data after the splitting being necessary for decoding, wherein in the second acceptance, a count value obtained by counting up for a duration of a long push against the display screen is accepted as the number of splits or the threshold, and wherein in the displaying the encryption target data, the count value is further displayed on the display screen. 